If you take some time to read Peters own blog about balancing videogames at
http://pqumsieh.com/. I kinda get the feel sometime that his perception of the overall problem with multiplayer balance is a compartmentalization between balancing teams and designers.
Now I don't work at relic so I have no idea about that, I just take it from the following. :
"I used to think design and balance were things that had to be done separate from one another.
This was reinforced by a similar sentiment which I encounter both at work and throughout the design community. That is not to say they are not both fields of design, but creating new content vs. balancing new content required completely different mind set. The designer is focused on creating innovative interesting decisions where the balancer is focused on making those decisions all equally appealing. The reason for this point of view is largely rooted in the belief that thinking about balance too early limits or restricts the creativity of the designer. I would imagine a number of colleagues might still share this belief, let me see if I can share some reasonable doubt to convince you otherwise."
Maybe, just maybe we shouldn't blame the balancing team for all that affects balance, but rather give try to understand that they sometimes cannot interfere at will with design choices. This would give a suitable explanation to why it sometimes takes a long time to 'fix' what seems to be blatant balance problems.
Maybe sometimes the balancing team are simply delivered "This is unit X it has Y and Z abilities, it should excel at A but be bad at B. Make sure you balance it but don't go do far from the overall design of the unit."
Same with factions.
But I digress again I don't know if too much compartmentalization is present at Relic or not, but thats the feeling I get.